1. Field of the Invention
The present invention relates to a provisional fixing structure for use in assembling an electronic tuner. More specifically, the present invention relates to a structure for provisionally fixing the respective components in an assembled state in assembling an electronic tuner.
2. Description of the Prior Art
FIG. 1 is a perspective view showing one example of an electronic VHF television tuner, in which the present invention can be advantageously employed. The electronic tuner 100 comprises the following principal components: a frame 1 serving as a shield casing; a circuit base plate 2 serving as a main base plate; an auxiliary base plate 3 serving as a shield and for connecting and fixing external connection terminals 4; shield plates 51 to 53; and cylindrical capacitor elements 6. The cylindrical capacitor elements 6 may comprise the so-called feedthrough capacitors, employing external connection terminals 4 as feedthrough conductors.
The frame 1 is made of a plate of conductive material such as iron, which comprises an elongated flat plate portion 11 extending in the vertical direction, and side plate portions 12 and 13 extending parallel to each other and crossing the above described flat plate portion 11 at substantially a right angle at both ends thereof. The free end of the side plate portion 12 is formed with pins 14 for fixing the tuner to a base plate, not shown, and the free end of the side plate portion 13 is formed with similar pins 15 for the same purpose. The flat plate portion 11 of the frame 1 is further formed with shield plate retaining portions 111a and 111b for retaining one end of each of shield plates 51 and 52. The side plate portion 12 is formed with a shield plate retaining portion 121 for retaining one end of shield plate 53. The auxiliary base plate 3 is fixed at the free ends of the frame 1, i.e. the free ends of the side plate portions 12 and 13.
The above described auxiliary base plate 3 is formed with a copper foil covering one entire surface thereof, as to be depicted in FIG. 12, to provide a shield effect. The auxiliary base plate 3 is formed with shield plate retaining portions 31a and 31b each corresponding to the above described shield plate retaining portions 111a and 111b, respectively. The end portions of the auxiliary base plate 3 are coupled and fixed to the free ends of the side plate portions 12 and 13.
In integrally assembling various components of electronic tuner 100, particularly the frame 1, the main base plate 2 and the auxiliary base plate 3, it is necessary to provisionally fix them in a united state before it is possible to secure them to each other permanently. Therefore, conventionally such approaches as shown in FIGS. 2, 3A and 3B are employed.
More specifically, referring to FIG. 2, the main base plate 2 is inserted into the frame 1 and then an auxiliary base plate 3 is brought to abut on the free ends of the side plate portions 12 and 13 of the frame. Then the abutting portions are provisionally fixed, by solder 7, for example. The approach shown in FIGS. 3A and 3B comprises formation of a pair of protrusions 71 at the free end of each of the side plate portions 12 and 13 of the frame 1. The auxiliary base plate 3 is positioned there, and the protrusions 71 are bent outward as shown in FIG. 3B, so that the auxiliary base plate 3 is caulked.
Besides the approaches shown in FIGS. 2, 3A and 3B, a further provisional fixing structure using bolting is employed. However, all of the conventional provisional fixing structures require incidental work, which makes a manufacturing process complicated and expensive. In particular, the approach employing soldering shown in FIG. 2 involves the problem that it is extremely difficult to achieve the desired provisional fixing in such a state that the frame 1, the main base plate 2, the auxiliary base plate 3, the external connection terminals 4 shown in FIG. 1, the shield plates 51 to 53, the feedthrough capacitor units 6 and the like are integrally united, without the auxiliary base plate 3 being inclined. Furthermore, the approach shown in FIGS. 3A and 3B employing caulking also involves the problem that it is extremely difficult to perform a caulking operation after such components as described above are integrally united, without damaging any components, particularly the base plate, and without using a jig.